System and method for detecting and correcting position deviations of an object having a curved surface

ABSTRACT

A position deviation system and method detects and corrects position deviations between the optical axis of an optical system, such as an exposure apparatus, and the center of a curved shaped object, such as a spherical shaped semiconductor. The system determines position deviations by illuminating the curved surface, passing light that is reflected off of the illuminated curved surface through a first lens having an optical axis and a first body. An image having a substantially central portion is formed on a surface using the reflected light. The position deviation is determined based on a position of the substantially central portion of the formed image relative to the optical axis.

CLAIM TO DOMESTIC PRIORITY

This application is a U.S. National Stage Application filed under 35U.S.C. 371 claiming priority from the International Application No.PCT/US2002/040788, filed Dec. 20, 2002, which application isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a system and method for detectingposition deviations of an object having one or more curved surfaces and,more particularly, to a system and method for detecting positiondeviations between the optical axis of the position deviation detectingsystem and the center of the object, such as a spherical semiconductor.

BACKGROUND OF THE INVENTION

Semiconductor devices are used in many types of products. Typically,semiconductor devices are manufactured by first growing generallycylindrical-shaped silicon (or other base semiconductive material)ingots. The ingots may then be sliced into generally flat, circularwafers; Through a variety of thermal, chemical, and physical processes,including diffusion, oxidation, epitaxial growth, ion implantation,deposition, etching, sputtering, polishing, and cleaning, active andpassive devices may be formed on one or both surfaces of the wafer. Thewafer may then be cut into individual rectangular semiconductor die,which may then be attached to a leadframe, encapsulated, and packaged asa discrete or integrated circuit. The packaged discrete and integratedcircuits may be mounted to printed circuit boards and interconnected toperform the desired electrical function.

More recently, another type of semiconductor integrated circuit device,known as a spherical shaped integrated circuit, has emerged. Sphericalshaped integrated circuits provide various advantages over conventionalflat integrated circuits. For example, the physical dimensions ofspherical integrated circuit allow it to adapt to many differentmanufacturing processes. Moreover, due to its shape, spherical shapedintegrated circuits shape have greater surface area as compared toconventional integrated circuits. Hence, a spherical integrated circuitmay have more (or larger) circuits and circuit elements formed on itssurface, as compared to a conventional, flat integrated circuit. Aspherical shaped integrated circuit may be manufactured by using avariety of conventional thermal, chemical, and physical processingsteps.

A system and method for manufacturing spherical shaped integratedcircuits is disclosed in U.S. Pat. No. 5,955,776 (“Ishikawa”). Inaccordance with Ishikawa, once the spherical semiconductor crystals areformed, each undergoes a variety of conventional thermal, chemical, andphysical processes. Thereafter, the circuit elements are formed in thespherical surface using the same basic processing steps that are used toform circuit elements on conventional, flat integrated circuits. Inparticular, a photoresist is applied to the surface of the sphere. Then,using an exposure apparatus, light from a light source is irradiatedthrough a mask onto the spherical surface. The mask has a circuitpattern formed on it and, as a result, this circuit pattern is projectedonto the surface of the spherical shaped semiconductor. The masked lightreacts with the photoresist to form the desired circuit on the surfaceof the sphere.

To ensure that the circuit pattern is projected on the surface of thespherical shaped semiconductor with sufficient precision, the center ofthe spherical shaped semiconductor should coincide with the optical axisof the exposure apparatus before exposing the surface to the maskedlight. One method of providing proper alignment is to form alignmentmarks on the surface of the spherical shaped semiconductor. Thesealignment marks are used to detect and correct any position deviations,and properly position the spherical shaped semiconductor on a supportstand. The support stand is then moved to the appropriate position inthe exposure apparatus, such that the optical axis of the exposureapparatus coincides with the center of the spherical-shapedsemiconductor.

Although the above-described positioning process generally works well,it does exhibit certain drawbacks. In particular, if the position of thealignment marks is sensed using an optical sensing device, it may not bepossible to detect position deviations with a sufficiently high degreeof sensitivity. This can be seen by referring to FIGS. 8 and 9. As FIG.8 illustrates, when the alignment mark 802 on the surface of thespherical shaped semiconductor 804 coincides with the optical axis 806of an optical system such as, for example, an exposure apparatus, thewidth of the alignment mark 802 is seen as being W0 by an opticalsensing device. Conversely, as FIG. 9 illustrates, a slightcounterclockwise rotation of the spherical shaped semiconductor 804causes a deviation (dy). If the spherical shaped semiconductor 804 isthen rotated clockwise so that the width of the alignment mark is seenas W0, then the deviation (dy) will still exist between the center ofthe alignment mark and the optical axis 806. Thus, the spherical shapedsemiconductor 804 may be translated until the center of the alignmentmark coincides with the optical axis 806, and the width of the alignmentmark is seen as being W1. For example, as illustrated in FIG. 9, when anincremental position deviation (“dy”) between the optical axis 806 ofthe optical system and the center of the spherical-shaped semiconductoris present, the distance from the principle plane of an object lens,represented in FIGS. 8 and 9 as a plane P1, to the surface of thespherical shaped semiconductor 804 becomes Z0+dz1 at one point, andZ0−dz2 at another point, compared to the proper distance of Z0. Duringexposure, such a difference of distance can cause the image of thecircuit pattern projected onto the surface of the spherical shapedsemiconductor to become unclear.

Another problem associated with the above-described positioning processis that it is not possible to correction any detected position deviationonce the spherical shaped semiconductor is mounted on the support standand positioned in the exposure apparatus. That is, after the sphericalshaped semiconductor is placed on the support stand and it is positionedwithin the exposure apparatus, there is a possibility that a positiondeviation may subsequently occur. The size of this position deviationdepends, at least in part, on the precision of the construction of themechanism that moves the support stand, making it extremely difficult tocomplete eliminate this possible movement.

Hence, there is a need for a system and method that detects and/orcorrects position deviations between the optical axis of an opticalsystem, such as an exposure apparatus, and the center of a sphericalshaped object, such as a spherical shaped semiconductor, that does notrely on an alignment mark formed on the surface of the object. There isadditionally a need for a system and method that detects and/or correctsposition deviations between the optical axis of an optical system andthe center of a spherical shaped object after the object is positionedwithin an exposure apparatus. The present invention addresses one ormore of these needs.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a system for detecting position deviationsof an object having a curved surface includes a first lens, a firstbody, an image formation device, and a moveable support. The first lenshas a first optical axis and a principle plane and is positioned toreceive and transmit therethrough light reflected from the curvedsurface. The first body has at least a portion thereof that issubstantially transparent to light and is positioned proximate the firstlens and is configured such that the first optical axis extendstherethrough, whereby at least a portion of the reflected light passesthrough the substantially transparent portion of the first body. Theimage formation device is positioned to receive the reflected lighttransmitted through the first lens and the substantially transparentportion of the first body and is operable to form a reflected imagebased on the received reflected light. The moveable support isconfigured to support the object and is operable to move the object inat least a first axis that is parallel to the first optical axis,whereby the object is moveable between at least two positions relativeto the principle plane of the first lens.

In another exemplary embodiment, a method of determining a positiondeviation of an object having a curved surface includes illuminating atleast the curved surface, and passing light that is reflected off of theilluminated curved surface through a first lens having a first opticalaxis and a first body having at least a portion thereof that issubstantially transparent to light. An image having a substantiallycentral portion is formed on a surface using the reflected light. Theposition deviation is determined based on a position of thesubstantially central portion of the formed image relative to the firstoptical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary position deviation detection systemaccording to a particular preferred embodiment;

FIG. 2 depicts the position deviation detection system of FIG. 1 withadditional detection and display components included therewith;

FIG. 3 illustrates the position deviation detection system of FIG. 2when the system is configured for exposure;

FIGS. 4A and 4B illustrates the position deviation detection system ofFIG. 2 when the system is configured for position deviation detection;

FIG. 5 is a simplified representation of the position deviationdetection system used to illustrate the principle of the presentinvention when there is no position deviation;

FIG. 6 is a simplified representation of the position deviationdetection system used to illustrate the principle of the presentinvention when there is a position deviation;

FIG. 7 illustrates an exemplary position deviation detection systemaccording to a particular alternative embodiment;

FIG. 8 illustrates a spherical shaped semiconductor that has aconventional alignment mark and when there is no position deviation; and

FIG. 9 illustrates the spherical shaped semiconductor of FIG. 10 whenthere is a position deviation.

DETAILED DESCRIPTION OF THE DRAWINGS

An optical system 100 that includes both a position deviation detectionsystem 110 and an exposure system 150 is shown in FIG. 1. In thedepicted embodiment, the position deviation detection system includes afirst lens 112, a stop ring 114, and an image formation device 116, allpositioned along a first optical axis 118. The first lens 112 ispreferably a convex lens having at least a principal plane P1. As willbe described more fully below, the first lens 112 functions to convergelight that is transmitted from a light source 122, via the stop ring114, onto a curved observation surface 124. The first lens 112 alsoconverges light that is reflected from the curved observation surface124 onto the image formation device 116, via the stop ring 114.

The stop ring 114 is positioned adjacent the first lens 112. In thedepicted embodiment, the stop ring 114 is positioned on the same side ofthe first lens 112 as the image formation device 116, and includes asubstantially circular inner circumferential surface 126 that forms anopening 128 through the stop ring 114. It will be appreciated that thestop ring 114 may be positioned on either side of the first lens 112.The stop ring 114 has at least two functions. The first function of thestop ring 114 is as a stop for adjusting the depth of field of the firstlens 112. The second function of the stop ring 114, which is describedin more detail further below, is as a “virtual alignment mark” fordisplaying the position of the center of the curved observation surface124 relative to the optical axis 118 of the position deviation detectionsystem 110. It will be appreciated that the stop ring 114 need notinclude the opening 128, but may instead have at least a portion that issubstantially transparent to the reflected light. It will also beappreciated that the stop ring 114 may be formed of various materialsincluding, but not limited to, metal, plastic, resin, or paper. Aportion of the stop ring surface may be blackened and/or its surface maybe microscopically roughened.

With the above-described configuration, light transmitted from the lightsource 122 is directed toward, and passes through, the stop ring 114 andthe first lens 112. Because it is a convex lens, the first lens 112causes the transmitted light to converge from the principle plane P1toward a first image plane P2 as it approaches the spherical observationsurface 124. When the spherical observation surface 124 is illuminatedwith this converged transmitted light, the spherical observation surface124 reflects at least some of the transmitted light back toward thefirst lens 112. This reflected light passes back through the first lens112 and the stop ring 114, forming a reflected image at a second imageplane P3. When the position of the image formation device 116corresponds to this second image plane P3, the reflected image isprojected onto the image formation device 116. In the depictedembodiment, the image formation device 116 is a semi-transparent screen.It will be appreciated that the position and magnification of the imageprojected onto the image formation device 116 is established based onthe distance between the first lens 112 and the curved observationsurface 124, and on the focal length of the first lens 112. It willadditionally be appreciated, and will be discussed in more detail below,that the particular image projected onto the image formation device 116depends upon the position of the curved observation surface 124 relativeto the first lens' principle plane P1, and upon the curvature ofobservation surface 124.

As FIG. 1 additionally depicts, the optical system 100 may additionallyinclude an exposure system 150. In the depicted embodiment, the exposuresystem 150 includes the light source 122, a second lens, 152, a mask154, and a half mirror 156, all positioned along a second optical axis158. It is noted that the light source 122 used in the exposure system150 is, in the depicted embodiment, the same light source 122 that isused in the position deviation detection system 110. It will beappreciated that the two systems need not share the same light source,and that two different light sources could be used. However, forefficiency and compactness of equipment size, the two systems preferablyshare the same light source.

The light source 122 generates diffuse light. Therefore, in the depictedembodiment, the second lens 152, which is a condensing lens, convertsthe diffuse light into parallel light rays. This parallel lightilluminates the mask 154, which has a prescribed circuit pattern (notillustrated) drawn on it. As such, the parallel light is transmitted orblocked in accordance with this circuit pattern. The half mirror 156 isconfigured at a predetermined angle (α) relative to the optical axis118. This predetermined angle (α) may be selected from any one ofnumerous angles, depending upon the configurations of the positiondeviation detection system 110 and the exposure system 150. In thedepicted embodiment, the predetermined angle (α) is approximately 45degrees. As with most half mirrors, the half mirror 154 in the exposuresystem 150 functions to separate the optical path of the positiondeviation detection system 110 and the optical path of the exposuresystem 150 from one another, even though at least a portion of theoptical axes of the two systems may overlap. It will be appreciated thatthe optical system 100 may also be configured without the second lens152.

Hence, when the exposure system 150 is being used, light from the lightsource 122 that is transmitted through second lens 152 and the mask 154is reflected by the half mirror 156. The mask 154 is positioned at afirst object plane P4 of the first lens 112. Thus, the light reflectedby the half-mirror 156 is transmitted through the stop ring 114 andfirst lens 112, and forms an image of the circuit pattern on the mask154 at the first image plane P2 (which corresponds to the object planeof the mask 154). If the position of the curved observation surface 124coincides with the first image plane P2 (as illustrated in FIG. 1), thecircuit pattern will be projected onto the curved observation surface124.

As was noted above, the curved observation surface 124 will reflect atleast some of the light transmitted onto it through the first lens 112.This reflected light forms an image at the second image plane P3, whichpreferably coincides with the image formation device 116. As was alsonoted above, the particular image formed at the second image plane P3will depend, at least in part, on the position of the curved surface 124relative to the first lens' principle plane P1. In particular, when thecurved surface 124 is positioned at the first image plane P2, thisposition coincides with a second object plane P5 (as shown in FIG. 1) ofthe first lens 112, and the image formed at the second image plane P3will be the curved surface 124. When the curved surface 124 is movedrelative to the first image plane P2, the second object plane P5 alsomoves, as will be described more fully below, and the image formed atthe second image plane P3 changes (this configuration is not shown inFIG. 1). For example, if the curved surface 124 is moved toward thefirst lens 112, such that the second object plane P5 corresponds to thestop ring 114, then an image of the stop ring 114 forms at the secondimage plane P3.

Turning now to FIG. 2, a particular embodiment of an optical system 200will be described. In particular, the depicted optical system 200 isused to detect and correct position deviations of spherical shapedsemiconductors 202, and to expose the spherical shaped semiconductors202 for circuit pattern formation on the surfaces thereof. It is notedthat in the following description, like reference numerals refer to likeparts of the optical system depicted in FIG. 1, and described above.

In addition to the components described and depicted in FIG. 1, theoptical system 200 depicted in FIG. 2 includes a support 204, a movementmechanism 206, a third lens 208, an image forming CCD element 212, adisplay 214, and a filter 216. The support 204 is a substantiallyhollow, tube-shaped device that has a first end coupled to the movementmechanism 206 and a second end 218 on which a spherical shapedsemiconductor is supported. In a particular preferred embodiment, afterthe spherical shaped semiconductor 202 is placed on the support 204, theinside of the support 204 is evacuated by, for example, a pump (notillustrated). With the inside of the support 204 at a vacuum, thespherical shaped semiconductor 202 is held in place on the support 204.

The support 204, as noted above, is coupled to the movement mechanism206. It is noted that the movement mechanism 206 is configured such thatthe spherical shaped semiconductor 202 may be moved both translationallyand rotationally. That is, it may be translated in the x-, y-, andz-axes, and rotated in the direction Ax-, Ay-, and Az-axes, all of whichare depicted in FIG. 2. It is noted that the movement mechanism 206 maybe any one of numerous devices known in the art for providing thisfunctionality, and that such a description is not necessary to anunderstanding of the present invention. Hence, a detailed description ofthe movement mechanism 206 will not be provided.

The third lens 208, the image forming CCD element 212, and the display214 comprise the image formation device for the optical system 200.Generally, the CCD element 212 optically functions similar to thesemi-transparent screen 116 depicted in FIG. 1. Because the area of theCCD element 212 is relatively small, the third lens 208 converges theluminous flux that is reflected from the spherical shaped semiconductor202, and through the first lens 112 and stop ring 114 toward the secondimage plane P3. It should be appreciated that the magnification of theimage that is formed on the CCD element 212 may be determined byselecting an appropriate combination of focal point distances of thefirst 112 and third 208 lenses. The image formed on the CCD element 212is converted into electrical data, which is transmitted to the display214. The display 214 receives the electrical data and displays the imageon a screen 218.

The filter 216 is moveable into, and out of, the second optical axis158. The filter 216 may be moved by any one of numerous manual orautomated devices and mechanisms 222. The particular device or mechanismused to move the filter 216 is not necessary to an understanding of thepresent invention and will, therefore, not be described further. Thefilter 216 functions to eliminate the particular light frequency(lies)to which the photoresist applied to the spherical shaped semiconductor202 is sensitive. For example, if the photoresist is sensitive toultraviolet (UV) light frequencies, the filter 216 will eliminate thesefrequencies while allowing other light frequencies to pass. Thus, whenthe position deviation detection system 110 is being used to detect andcorrect position deviations, the filter 216 is moved into the secondoptical axis 158. As a result, the spherical shaped semiconductor 202may be illuminated by the light source 122 with light frequencies thatdo not react with the photoresist. Thereafter, following any positiondeviation corrections, the filter 216 is moved out of the second opticalaxis 158, which allows the exposure operation to be properly completed.

Having described the configuration of optical system 100, including boththe position deviation detection system 110 and the exposure system 150,and the functions of the various components that make up these systems,a description of the method by which the position deviation detectionsystem 110 detects a position deviation will now be provided. In doingso, the method will first be described generally, followed by a moredetailed description.

First, with the light source 122 emitting light rays and the filter 216positioned in the second optical axis 158, the movement mechanism 206moves the spherical shaped semiconductor 202 in the z-axis. When thesurface of the spherical shaped semiconductor 202 reaches a firstpredetermined position, which coincides with the first image plane P2,the surface of the spherical shaped semiconductor 202 is reflected ontothe CCD element 212 and is displayed on the display screen 218.Thereafter, the spherical shaped semiconductor is moved in the z-axiscloser to the first lens 112. At a second predetermined position, theimage of the stop ring inner circumferential surface 126 that isreflected by the surface of the spherical shaped semiconductor 202 isinstead reflected onto the CCD element 212 and is displayed on thedisplay screen 218. Depending on the particular structure of the stopring 114, the image of the stop ring 114 may be seen as a “shadow” onthe display screen 218, and the image of the opening formed by the innercircumferential surface 126 may be seen as a “circle of light” on thedisplay screen 218. No matter the case, if the center of this reflectedimage 402 is displayed in the center of the display screen 218 (see FIG.4A), then the center of the spherical shaped semiconductor 202 isaligned with the first optical axis 118, and there is no positiondeviation. Conversely, if the center of this reflected image 402 isdisplayed in an off-center position of the display screen (see FIG. 4B),then the center of the spherical shaped semiconductor 202 is not alignedwith the first optical axis 118, and there is a position deviation. If aposition deviation is detected, the movement mechanism 206 can then movethe spherical semiconductor 202 in the appropriate axes to correct theposition deviation. This position deviation correction may be carriedout by manual or automatic manipulation of the movement mechanism 206.

It is additionally noted that the actual amount of position deviation isproportional to the amount of position deviation that is displayed onthe display screen 218. Thus, the actual amount of position deviationcan be automatically measured using the displayed position deviation. Todo so, an image processing system 250, which is depicted in phantom inFIG. 2, may be added to the optical system 100. The image processingsystem 250 may be any one of numerous such systems known in the art. Ina particular preferred embodiment, the system disclosed in U.S. Pat. No.6,148,270, may be used. With this system 250, the reflected image 402with no position deviation is recorded. Then, the image 402 with aposition deviation is read into the image processing system 250. Theimage processing system 250 then determines the actual amount ofposition deviation by comparing the two images.

Turning now to FIGS. 3-6, a more detailed description will be providedas to why the above-described method for determining position deviationworks in the manner described. First, FIG. 3 shows a state where thespherical shaped semiconductor 202 is positioned such that its surfacecoincides with the first image plane P2 (z₀). Thus, the surface of thespherical shaped semiconductor 202 is reflected onto the CCD element 212and is displayed on the display screen 218. It should be noted that theparticular spherical shaped semiconductor 202 shown in FIG. 3 does notyet have a circuit pattern formed thereon. Hence, a blank image isdisplayed on the display screen 218.

Next, FIGS. 4-6 show a state where the surface of the spherical shapedsemiconductor 202 has been moved to a second position (z₁) that iscloser to the first lens 112, for performing position deviationdetection. In this position, the second object plane P5 of the firstlens 112 no longer coincides with the first image plane P2 and thesurface of the spherical shaped semiconductor 202. Instead, the secondobject plane P5 coincides with the stop ring 114. As shown more clearlyin FIGS. 5 and 6, the surface of the spherical shaped semiconductor 202behaves like a convex mirror, having a center of curvature of “r” and afocal point 502 located at “r/2.” For clarity, in FIGS. 5 and 6, thethird lens 208 is omitted, since it functions merely to adjust imagemagnification on the CCD element 212. The first lens 112 is depicted asthe principal plane P1, and the CCD element 212 is depicted as thesecond image plane P3. As is generally known in the art, the imagesformed by a convex mirror are sometimes referred to as “virtual images”because the images appear where the light rays reflected by the mirrorseem to diverge from the focal point behind the mirror, which, in thisinstance is the focal point 502 within the spherical shapedsemiconductor. Thus, as was noted above, as the position of thespherical shaped semiconductor 202 changes in the z-axis, for example,from a first position z₀ to a second position z₁ (dz=|z₁−z₀|), theposition of the second object plane P5 also changes.

For ease of explaining the principle of virtual images, it is possibleto consider the spherical shaped semiconductor 202 as a concave lens,which is optically equivalent to a convex mirror. Thus, in FIGS. 4A and4B the spherical shaped semiconductor 202 is replaced with a convex lens404, which produces a virtual image on the lower side (as viewed in FIG.4) of the convex lens. In FIG. 4A, the virtual image 406, which isillustrated using solid lines, occurs when the center of the sphericalshaped semiconductor 202 coincides with the first optical axis 118.Thus, the virtual image 406 is symmetric to the real image formed on thefirst optical axis 118. This same configuration is what is illustratedin FIG. 5. That is, the center 504 of the spherical shaped semiconductor202 is aligned with the first optical axis 118. Thus, light from thelight source 122 passes through the stop ring 114 and first lens 112(e.g., P1), is reflected by the spherical shaped semiconductor 202, backthrough the first lens 112 and stop ring 114, and forms an image on theCCD element 212 (e.g., P3), via the third lens 208 (not illustrated inFIG. 5). Because the center of the stop ring 114 and the center 504 ofthe spherical shaped semiconductor 202 are both aligned along the firstoptical axis 118, the reflected image formed on the CCD element 212(e.g., P3) and displayed on the display screen 218 is centered, asdepicted in FIG. 4A.

The virtual image 408 in FIG. 4B, occurs when there is a deviationbetween the center of the spherical shaped semiconductor 202 and thefirst optical axis 118. In this case, the virtual image 408 has aninclination angle (β) relative to the first optical axis 118. In thismanner, the position deviation of the spherical shaped semiconductor 202is observed as a deviation of the virtual image 408 from first opticalaxis 118. This same configuration is what is illustrated in FIG. 6. Thatis, the center 504 of the spherical shaped semiconductor 202 isdisplaced from the first optical axis 118 by an incremental amount(“dy”). Again, light from the light source 122 passes through the stopring 114 and first lens 112 (e.g., P1), is reflected by the sphericalshaped semiconductor 202, back through the first lens 112 (e.g., P1) andstop ring 114, and forms an image on the CCD element 212 (e.g., P3), viathe third lens 208 (not illustrated in FIG. 8). In this case, however,because the center 504 of the spherical shaped semiconductor 202 isdisplaced from the first optical axis 118, the image formed on the CCDelement 212 (e.g., P3) and displayed on the display screen 218 is notcentered. Instead, as shown in FIGS. 4 and 6B the displayed image 402 isdeviated from center by an amount (“dyr”) that corresponds to the actualdeviation of the spherical shaped semiconductor 202.

As was previously noted, the position of the spherical shapedsemiconductor 202 may be corrected each time the above-describedposition deviation detection method is performed. By detecting andcorrecting the position of the spherical shaped semiconductor 202, thespherical shaped semiconductor 202 can be positioned with asubstantially high degree of precision. After the spherical shapedsemiconductor 202 is properly positioned, as shown in FIG. 2, the filter216 may be removed from the second optical axis 158 and, if not done soalready, the mask 154 is then positioned in the second optical axis 158.This allows the UV rays emitted by the light source 122 to betransmitted through the mask 154, reflected off the half mirror 156, andto pass through the stop ring 114 and first lens 112, to thereby projecta wiring pattern on the surface of the spherical-shaped semiconductor202. Since the first optical axis 118 and the center of the sphericalshaped semiconductor 202 coincide, the wiring pattern projected on thesurface of the spherical shaped semiconductor 202 is not warped.

An alternate embodiment of an optical system is depicted in FIG. 7. Thesystem 700 illustrated in FIG. 7 is similar to that illustrated in FIG.1, with the following differences: (1) the optical system of theposition deviation detection system 110 has been bent by the half mirror156; (b) a pattern generator 702 is used to provide a mask in theexposure system 150; and (c) the position of the light source 122 isdifferent. The pattern generator 702 may be a conventionally knowngenerator, in which multiple mirrors are arranged in a grid, and areon-off controlled. An example of such a pattern generator is sold byTexas Instruments under the product names Digital Mirror Device (“DMD”)and Digital Light Processor (“DLP”). A photolithography technique thatemploys this type of pattern generator is disclosed in U.S. Pat. No.6,251,550. Because the position deviation detection method in thisembodiment is the same as that in the previous embodiment, furtherdiscussion thereof is omitted.

It should be appreciated that the present invention is not limited toconfigurations that include the exposure systems 150 illustrated inFIGS. 1, 2 and 7, but could be configured to include only the positiondeviation detection system 110. It will be further appreciated that ifthe system is indeed configured solely as a position deviation detectionsystem 110, the position of the light source 110 may be varied from thepositions shown in FIGS. 1, 2 and 7. For example, the light source 122may be positioned proximate the stop ring 114 at any one of numerouspositions off of the first optical axis 118, so long as the lowersurface of the stop ring 114 is illuminated.

It will additionally be appreciated that the present invention is notlimited to use of the stop ring 114 for providing a “virtual mark.”Examples of other devices include, but are not limited to, a reticule, arelatively thin stick, or a relatively thin slab. In addition, thepresent invention is not limited to detecting position deviationsrelative to the first optical axis 118. For example, position deviationsmay be detected on one side of the first optical axis 118. Moreover, theposition of the device that provides the “virtual mark” relative to thefirst optical axis 118 may also be varied. For example, it may bepositioned anywhere within the range of the object plane distance of thefirst lens 112. It will be further appreciated that the first 112,second 152, and third 218 lenses may each be formed as single pieces, ormay be formed as an assembly of lenses that together function as aconvex lens.

In addition to the varying configurations of the system describedimmediately above, it will be appreciated that the position deviationdetection system and method disclosed herein is not limited to sphericalshaped semiconductors, or other objects that are spherical shaped orhave surface contours, or portions thereof, that are spherical. Rather,the shape of the object need only have a surface, or portion thereof,with a curved contour, which may be symmetric or axisymmetric. Forexample, position deviations of objects shaped as a column, a rotatingelliptical surface, a rotating parabolic surface, and so on, may also bedetected.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt to a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe appended claims.

1. A system for detecting position deviations of an object having a curved surface, comprising: a first lens having a first optical axis and a principal plane, the first lens positioned to receive and transmit therethrough light reflected from the curved surface; a first body having at least a portion thereof that is substantially transparent to light, the first body being positioned proximate the first lens and configured such that the first optical axis extends therethrough, whereby at least a portion of the reflected light passes through the substantially transparent portion of the first body; an image formation device positioned to receive the reflected light transmitted through the first lens and the substantially transparent portion of the first body and operable to form a reflected image based on the received reflected light; and a moveable support configured to support the object and operable to move the object in at least a first axis that is parallel to the first optical axis, whereby the object is moveable between at least two positions relative to the principal plane of the first lens.
 2. The system of claim 1, further comprising: a light source operable to supply light, wherein the first lens is positioned to receive the light supplied by the light source and transmit the received light onto the curved surface.
 3. The system of claim 1, wherein the image formation device comprises: a CCD element operable to receive the reflected light and convert it into electrical data representative of the reflected image; and a display coupled to receive the electrical data and operable to display the reflected image.
 4. The system of claim 1, wherein: the curved surface has a center of curvature; and the reflected image has a substantially central portion that is formed on the image formation device at a position that is representative of a position deviation of the center of curvature relative to the first optical axis.
 5. The system of claim 4, wherein the moveable support is further operable to move the object to thereby substantially eliminate any position deviation.
 6. The system of claim 1, further comprising: a light source operable to supply light along a second optical axis; a half-mirror configured at a predetermined angle relative to the first and second optical axes and operable to reflect the supplied light along the first optical axis toward the first lens and to allow the reflected light to pass therethrough toward the image formation device.
 7. The system of claim 6, further comprising: a mask having at least a portion thereof positioned between the light source and the half-mirror along the second optical axis, whereby a circuit pattern is formed on the curved surface.
 8. The system of claim 7, further comprising: a light filter moveable into and out of the second optical axis between the light source and the mask, the light filter operable to remove predetermined light frequencies transmitted from the light source.
 9. The system of claim 7, wherein the mask is a pattern generator.
 10. The system of claim 7, further comprising: a second lens positioned between the light source and the mask along the second optical axis.
 11. The system of claim 1, further comprising: a third lens positioned between the first body and the image formation device along the first optical axis.
 12. The system of claim 11, wherein the first and third lenses are each convex lenses.
 13. The system of claim 1, wherein the image formation device is positioned along a third optical axis having a predetermined angle relative to the first optical axis, and wherein the system further comprises: a half mirror configured at a predetermined angle relative to the first and third optical axes and operable to reflect the light that is reflected from the curved surface along the third optical axis toward the image formation device.
 14. The system of claim 13, further comprising: a light source operable to supply light, wherein the half mirror is further operable to allow the supplied light to pass therethrough along the first optical axis toward the first lens.
 15. The system of claim 1, wherein the first body is a stop ring that includes an opening formed therein that is substantially circular in shape and has a predetermined diameter.
 16. A method of determining a position deviation of an object having a curved surface, comprising: illuminating the curved surface; passing light that is reflected off of the illuminated curved surface through a first lens having a first optical axis and a first body having a portion thereof that is substantially transparent to light; forming an image having a substantially central portion on a surface using the reflected light; determining the position deviation based on a position of the substantially central portion of the formed image relative to the first optical axis; and displaying the position deviation on a display screen.
 17. The method of claim 16, further comprising: illuminating the curved surface with light from a light source.
 18. The method of claim 17, further comprising: passing the light through the first lens and onto the curved surface.
 19. The method of claim 16, further comprising: displaying the reflected image on a display device.
 20. The method of claim 16, wherein: the curved surface has a center of curvature, and wherein the image is formed at a position that is representative of a position deviation of the center of curvature relative to the first optical axis.
 21. The method of claim 16, further comprising: moving the object to thereby substantially eliminate any position deviation.
 22. The method of claim 16, further comprising: supplying light along a second optical axis; reflecting the light supplied along the second axis such that the light is supplied light along the first optical axis and is directed toward the curved surface for illumination thereof.
 23. The method of claim 22, further comprising: passing the supplied light through a mask to form a circuit pattern on the curved surface.
 24. The method of claim 23, further comprising: selectively filtering the supplied light before it passes through the mask.
 25. The method of claim 22, further comprising: passing the supplied light through a second lens positioned along the second optical axis.
 26. The method of claim 16, further comprising: passing the reflected light through a third lens that is along the first optical axis. 